1. Field of the Invention
This invention generally relates to a reader printer apparatus and more particularly to a reader printer apparatus for viewing microimages and alternatively printing microimages on standard 81/2.times.11 plain paper which includes a molded modular housing which allows components to be secured directly thereto, thereby obviating the need for various metal chassis and brackets which significantly reduces the overall weight of the machine and a scanning mechanism that is synchronized to the speed of the print engine but, mechanically independent from the print engine in order to reduce distortions in recorded images due to speed fluctuations in the print engine motor due to wear or voltage fluctuations.
2. Description of the Prior Art
Various reader printer apparatus are known in the art. An example of such an apparatus is disclosed in U.S. Pat. No. 4,783,685. Such apparatus are utilized for displaying and printing microimages formed on microfilm, microfiche and the like. Such apparatus normally include an injection molded outer housing formed from an injection molded plastic material. Since such a process can only yield wall thicknesses that are approximately one hundred thousandths inches thick, the housings formed from such a process do not have the structural integrity to support the various components within the apparatus. Consequently, such reader printer apparatus are generally provided with various metal chassis and brackets, rigidly secured within the injection molded housing for carrying the various components within the reader printer apparatus. Such metal chassis and brackets add considerable weight to the machine, which, in turn, can lead to a relatively heavier apparatus, which is not only more cumbersome to handle but results in increased cost due to the additional components. In addition, such apparatus result in increased shipping costs. More specifically, such machines which utilize various metal chassis and brackets typically weigh about one hundred pounds. It is generally well known that shipping articles that weigh more than seventy pounds often have to be shipped by truck, which can be relatively expensive. On the other hand, articles which weigh less than seventy pounds can be shipped by small package carriers, such as United Parcel Service, at a substantially lower cost.
Another problem with reader printer apparatus as described in the aforementioned U.S. patent relates to the scanning mechanism. More specifically, such an apparatus utilizes a slit exposure type image recording method for printing the microimage. In a slit exposure type printing apparatus, the image is formed on a printing drum in sections by scanning consecutive portions of the microimage. The image is scanned by a scanning mechanism which includes a print mirror that is rotated during a print cycle to consecutively form the image on the print drum. In such a system, the rotatable print mirror is mechanically driven from the print drum in order to synchronize the scanning speed with the speed of the print drum.
As is known in the art, the scanning speed of the scanning box mechanism must be kept relatively constant. However, due to wear on the print engine, the scan box mechanism does not always run at a constant speed over the life of the engine. Moreover, gear runout in the engine drive mechanism is not the same for each engine. Consequently, runout over the life of the engine can cause erratic movement of the scan box mechanism when scanning. Since the scanning mechanism is mechanically driven from the print engine, such variations in the engine drive mechanism can result in recorded images that are out of focus.
There are other problems associated with the reader printer apparatus as disclosed in the aforementioned U.S. patent. These problems relate to the position of the scanning mechanism relative to the object plane (e.g., the plane defined by the microfiche after it is inserted into the machine for viewing or printing). In the reader printer apparatus disclosed in the aforementioned U.S. patent, the scanning mechanism is disposed about half way between the object plane and the image plane (e.g., the plane defined by the printed image, for example, on the print drum). By disposing the scanning mechanism midway between the object plane and the image plane, the overall length of the machine is increased. Moreover, in such an apparatus, the optical paths during a viewing mode and a printing mode overlap which results in the need to provide movably mounted viewing mirrors that are moved out of the optical path during a printing mode.